There has been conventionally known an AlGaInP light emitting element as shown in FIG. 3. In the light emitting element H101 shown in said Figure, a light emitting part A101 having a double heterostructure wherein an n-type AlGaInP cladding layer 102, an AlGaInP active layer 103 and a p-type AlGaInP cladding layer 104 are sequentially laminated, is formed on an n-type GaAs substrate 101, and an electrode contact layer 107 is formed via a p-type AlGaAs protecting layer 106 on said light emitting part A101. A GaAs layer permitting easy formation of an ohmic contact is used as the electrode contact layer 107.
The above-mentioned structure of the semiconductor light emitting element H101 is advantageous in that occurrence of distortion due to different lattice constants is less, whereas the light emitted from the active layer 103 is absorbed by the uppermost GaAs layer 107 having a band gap of 1.42 eV. Therefore, the absorption of the light is suppressed by removing portions of the layer 107 other than the part right beneath the electrode by selective etching.
The etching of the GaAs layer 107 in the above-mentioned light emitting element H101 increases manufacture steps and production costs. In addition, the portion without the GaAs layer 107 becomes easily oxidized, since the AlGaAs layer 106 is exposed, thus causing problems in terms of moisture resistance. For overcoming this problem, a moisture-resistant layer needs to be formed separately, which increases steps and cost.
On the other hand, an AlGaInP light emitting element structure comprising an electrode contact layer 207 which does not require removing by etching, as shown in FIG. 4, has also been known. The light emitting element H201 shown therein comprises a p-type GaP contact layer 207 formed as an electrode contact layer on a light emitting part A201 having the same double heterostructure as the light emitting part A101 shown in the above-mentioned FIG. 3.
This light emitting element structure, however, is subject to occurrence of interfacial distortion between the GaP layer 207 and the AlGaInP cladding layer 204 thereunder, due to the different lattice constants and coefficients of thermal expansion of these layers. Specifically, the GaP layer 207 generally formed in the thickness of about 10 .mu.m shows greater distortion, causing a load applied to the light emitting part A201, and said load lowers light emission efficiency and shortens service life. This problem becomes prominent with increasing thickness of the GaP layer 207.